Continuously variable power-branched transmission, and a method for regulating a continuously variable power-branched transmission

Abstract

A continuously variable power-branched transmission for a motor vehicle, including an input shaft, a variable speed drive unit having pairs of conical disks and a continuously variable transmission ratio, a gear system, and an output shaft. Two control clutches connect the variable speed drive unit and the gear system so that when going through the entire transmission ratio range of the power-branched transmission the adjustment range of the variable speed drive unit is passed through a plurality of times. The transmission also includes rotational speed sensors and a controller that determines whether a change in rotational speed is triggered by a change in the transmission ratio, and when it is not triggered by a change in the transmission ratio, the controller adjusts the variable speed drive unit so that the change in rotational speed not triggered by a change in the transmission ratio is compensated.

1. A continuously variable power-branched transmission for a motor vehicle, said transmission comprising: an input shaft drivable by an engine to provide an input torque; a variable speed drive unit operatively connected with the input shaft and having a continuously variable transmission ratio and including two pairs of axially opposed conical disks wherein a spacing between the disks of a disk pair is axially adjustable; a gear train operatively coupled with the variable speed drive unit and including an output shaft; at least two control clutches for connecting shafts of the variable speed drive unit with the gear train so that when going through the entire transmission ratio range of the power-branched transmission an adjustment range of the variable speed drive unit is passed through a plurality of times; axial force producing means for producing an axial force to reposition one conical disk of a conical disk pair of the variable speed drive unit to adjust the transmission ratio of the variable speed drive unit; means for detecting a change in rotational speed of respective shafts; and a controller operatively connected with the transmission and adapted to make a differentiation as to whether a change in rotational speeds of the shafts is triggered by a change in the transmission ratio, and when the rotational speed change is not triggered by the change in the transmission ratio, to change an axial force imposed by the axial force producing means to compensate for the change in rotational speed that is not triggered by a change in the transmission ratio. 
   
   
     2. A transmission in accordance with  claim 1 , including torque detection means for detecting an input torque to the transmission. 
   
   
     3. A transmission in accordance with  2 , wherein the controller is adapted to make a judgment as to whether a change in rotational speed ratio is triggered by the change in the transmission ratio by means of a torque that is detected by the torque detection means. 
   
   
     4. A transmission in accordance with  claim 2 , wherein the torque detection means is adapted to transmit a torque signal to the controller in one of electrical and hydraulic form. 
   
   
     5. A transmission in accordance with  2 , wherein the controller carries out the following steps when the change in rotational speed is detected:
 a) determining the torques of active shafts of the power-branched transmission using the current transmission ratio of the transmission and shaft inertial masses; 
 b) determining a torque conducted through the variable speed drive unit; 
 c) determining a necessary axial force of the axial force producing means from the torque conducted through the variable speed drive unit; 
 d) determining the torque conducted through the torque detection means; 
 e) determining a produced axial force from the torque contribution determined in step (d); 
 f) calculating the difference between the necessary axial force and the produced axial force; and 
 g) ordering a change in axial force of the axial force producing means so that the difference calculated in step (f) decreases. 
 
   
   
     6. A transmission in accordance with  claim 5 , wherein the transmission includes a plurality of rotational speed sensors, and a determination is carried out in at least one of the steps a) through e) based upon rotational speed signals from the rotational speed sensors to determine the transmission ratio of the variable speed drive unit. 
   
   
     7. A transmission in accordance with  claim 5 , wherein in at least one of the steps a) through e) the transmission ratio of the overall transmission is utilized by the controller. 
   
   
     8. A transmission in accordance with  claim 5 , wherein in at least one of the steps a) through e) shift states of the at least two control clutches are conveyed to the controller. 
   
   
     9. A transmission in accordance with  claim 5 , including a rotational speed sensor for detecting rotational speed of the vehicle wheels, and wherein in at least one of the steps a) through e) a change in the rotational speed of the vehicle wheels detected by the rotational speed sensors for the rotational speeds of the vehicle wheels is conveyed to the controller. 
   
   
     10. A method for regulating a continuously variable power-branched transmission for a motor vehicle, wherein the transmission includes an input shaft drivable by an engine, a variable speed drive unit with continuously variable transmission ratio, a gear system operatively connected with the variable speed drive unit and having an output shaft, at least two control clutches for connecting the variable speed drive unit and the gear system to each other so that when proceeding through the entire transmission ratio range of the power-branched transmission an adjustment range of the variable speed drive unit is passed through a plurality of times, axial force producing means for producing an axial force to reposition one conical disk of a conical disk pair to adjust the transmission ratio of the variable speed drive unit, means for detecting a change in rotational speed of a shaft, and a controller, said method comprising the steps of:
 detecting a change in rotational speed of a shaft; 
 determining whether the change in rotational speed is triggered by the change in the transmission ratio; and 
 if the change in speed of rotation is not triggered entirely by the change in the transmission ratio, changing an axial force applied to the one conical disk by the axial force producing means to compensate for the change in rotational speed that is not triggered by a change in the transmission ratio. 
 
   
   
     11. A method in accordance with  claim 10 , including the step of detecting a torque by a torque detection means for producing a contact pressure of the conical disks with an endless torque-transmitting means that is proportional to the torque being transmitted. 
   
   
     12. A method in accordance with  claim 11 , wherein the controller makes a judgment as to whether the change in the rotational speed ratio is triggered by the change in the transmission ratio, by means of a torque that is detected by the torque detection means. 
   
   
     13. A method in accordance with  claim 11 , including the step of transmitting to the controller a torque signal from the torque detection means, wherein the torque signal is one of electrical form and hydraulic form. 
   
   
     14. A method in accordance with  claim 11 , wherein the controller carries out the following steps when the change in rotational speed is detected:
 a) determining the torques of active shafts of the power-branched transmission, using the current transmission ratio of the transmission and inertial masses of the shafts; 
 b) determining the torque conducted through the variable speed drive unit; 
 c) determining the necessary axial force of the axial force producing means from the torque conducted through the variable speed drive unit; 
 d) determining the torque conducted through the torque detection means; 
 e) determining the produced axial forces from the torque contribution determined in (d); 
 f) calculating the difference between the necessary and the produced axial forces; and 
 g) ordering a change in axial force such that the difference in (f) decreases. 
 
   
   
     15. A method in accordance with  claim 14 , wherein the transmission includes a plurality of rotational speed sensors, and a determination is carried out in at least one of the steps a) through e) based upon rotational speed signals from the rotational speed sensors to determines the transmission ratio of the variable speed drive unit. 
   
   
     16. A method in accordance with  claim 14 , wherein in at least one of the steps a) through e) the transmission ratio of the overall transmission is conveyed to the controller. 
   
   
     17. A method in accordance with  claim 14 , wherein in at least one of the steps a) through e) a shift state of the at least two control clutches is conveyed to the controller. 
   
   
     18. A method in accordance with  claim 14 . wherein a rotational speed sensor is provided for sensing rotational speeds of the vehicle wheels, and wherein in at least one of the steps a) through e) a change in the rotational speeds of the vehicle wheels detected by the rotational speed sensors for the vehicle wheels is conveyed to the controller. 
   
   
     19. A transmission in accordance with  claims 2 , wherein the torque detection means is a hydromechanical torque sensor that produces a pressure on a conical disk that is proportional to the torque being transmitted.